This invention relates generally to a method and apparatus for measuring the distribution of radioactivity. More particularly, the present invention relates to a method and apparatus for measuring the distribution of radioactivity which is suitable for measuring the intensity distribution of radioactivity of nuclides existing inside an object to be measured whose internal structure is not known.
Conventional methods of measuring radioactivity are disclosed, for example, in Japanese Patent Laid-Open No. 40978/1974 and EPC Laid-Open No. 114968 (which corresponds to U.S. patent application Ser. No. 555,613, U.S. Pat. No. 4,591,720). The method of the Japanese prior art reference measures radioactivity of a body by moving up and down a pair of radiation sensors, while the method of the EPC prior art reference measures the contamination of the body surface and internal contamination of people to be measured and distinguishes the kind of radioactive nuclides on the basis of the ratio of a photoelectric effect component to a Compton scattering component obtained by the analysis of the peak of an output signal of a radiation sensor. If the contamination is judged to be internal contamination, the internal dose rate of a subject to be measured is determined.